This invention relates to an overheat protector for use in a variety of electric instruments or appliances. The overheat protector according to the invention is well adaptable for use in a dc-to-dc converter, although no unnecessary limitations to this particular application are intended.
Dc-to-dc converters and the like have so far been protected against overheating by use of temperature sensors such as thermostats and thermistors. The thermistor is classifiable into two types—positive temperature coefficient (PTC) and negative temperature coefficient (NTC). The PTC thermistor is known as a posistor (tradename). As currently placed on the market, the thermostats, thermistors and posistors are all too expensive for the applications envisaged by the instant invention, by reasons of limited productions and very fine temperature control offered. These familiar temperature sensors have therefore added substantively to the manufacturing costs of overheat protectors, as well as to those of the dc-to-dc converters or the like incorporating such protectors.
Use of the Schottky-barrier diode for temperature sensing has recently been suggested by Japanese Unexamined Patent Publication No. 2001-45655. It teaches to measure temperatures on the basis of the temperature-dependent reverse current of a Schottky-barrier diode, switching off the power supply upon detection of a reverse current magnitude in excess of a predetermined limit. This unexamined patent application is silent, however, on how the Schottky-barrier diode is used in an actual dc-to-dc converter or other electric instrument of the type having a current controller and associated control circuit therefore.